The park will offer free Discovery cave tours, 10:00 a.m.-2:00 p.m., in honor of National Public Lands Day. Pick up a free ticket at the visitor center, then walk down the hill to the Historic Entrance for this self-guided tour. The tour requires a walk down and up the steep hill below the visitor center, as well as 160 steps. Visit the Rotunda, one of the largest rooms, explore a vast canyon passageway, and learn about 19th-century saltpeter mining operations and the geologic origins of Mammoth Cave on each of these tours. Walk at your own pace, allowing at least 30 minutes; about 3/4 mile round trip.

Note: cave tour requirements regarding white-nose syndrome (WNS) in bats: While there are no known harmful effects to humans, WNS is responsible for the death of millions of hibernating bats across the eastern United States since its discovery in 2006. WNS was found in Mammoth Cave in winter 2012-13. To minimize the spread of WNS fungus, all participants on cave tours must walk across bio-security mats to clean footwear immediately following the conclusion of their tour.

The Mammoth-on is America's only cave, hike, and bike triathlon. The Mammoth-on begins with a ranger-led hike in Mammoth Cave, followed by a two-mile unescorted woodland hike. The final leg is a bike ride along the gravel Mammoth Cave Railroad Hike and Bike Trail to Park City, a maximum ride of 20 miles round trip.

Register for either of the Friends events via Facebook/MammothFriends; $25 per person, family rate is available.

For more informationcall 270-758-2152, or by email at friends.mammoth.cave@gmail.com